Control apparatus



April 6, 1943. p. HAYMOND 2,316,066

CONTROL APPARATUS Filed Aug. 5, 1940 2 SheetS-Shee't 1 r iw m`:" k 72 x w 5 :a 34 m 181 *27 JL FL INVENTOR April 6, 1943. P HAYMOND 2,316,066

CONTROL APPARATUS Filed Aug. 3, 1940 2 Sheets-Shea*l 2 INVENTOR ATTORNEY 1 actuated by the snap mechanism.

Other and further objects and advantages- Patented Apr. 6, 1943 UNITED STATES PATENT OFFICE Paulclgxm va. Y Application Angius 3,1940, semi No. 350,889 l 1s claims. (ci. ca -4N The present invention relates to control apparatus, and particularly to control apparatus for -refrigerating systems.

' An object of the invention is to provide a valv for controlling the flow of refrigerant through the evaporator of a refrigerating system, which valve is operated to increase and decrease the ow of refrigerant through the evaporator in accordance with predetermined temperatures produced in Y one part of the system, as for example the evaporator, and providing a device actuated in ac' cordance with the changes in .temperature in another part of the system, for example the air .valve for controlling the flow of refrigerant through the evaporator of a refrigerating system, which valve is adapted to be operated by a device in accordance with temperature changes in the evaporator, and providing mechanism for maintaining the valve in the open positionregardless of the temperature in the evaporator as long as the temperature in the medium cooled by the evaporator is above a predetermined temperature.

Still another object of the invention is to provide a controller for a refrigerating system, which controller includes a control member that is operated in accordance with temperatures produced in one part of the system and an electrically responsive latch mechanism for preventing movement of the control member to one of its control positions, and which electrically responsive latch mechanism is controlled by a thermostat operable in accordance with the temperature in another part of the system for releasing the control member when the temperature in the latter part of the system attains a predetermined temperature.

A still further object of the invention is to provide a snap mechanism for operating a valve for controlling the flow of refrigerant through the evaporator of a refrigerating system, and a switch for controlling operation of the refriger ant condensing mechanism, which switch also is will be apparent from the following description, reference being had to the accompanying drawings wherein a preferred form of embodiment of the present invention is clearly shown.

In the drawings:

Fig. `1 is a diagrammatic illustration of a refrigerating system and control apparatus therefor;

Fig. 2 isA a view on a larger scale, and partly in section, of a control apparatus shown in Fig. 1, and

Fig. 3 is a view of a snap mechanism taken on substantially line 3 3 of Fig. 2.

Referring to the drawings, the invention is shown embodied ina refrigerating system indicated generally at 20, however, the invention may be embodied in different forms of refrigerating systems.` 'I'he refrigerating system 20 is a compressor-condenser-expander type and includes two evaporators 2| and 22, a compressor 24 and a condenser 25. The compressor 24 is driven by an electric motor 26 and withdraws refrigerant from the evaporators and directs compressed refrigerant to the condenser 25 from whence condensed refrigerant is conducted to the evaporator 2| by a pipe 21 and to the evaporator 22 Yby a pipe 29, which pipe taps pipe 21. Conventional expansion valves 30 and 3| are provided at the inlets of the evaporators, although iloat valves could be employed. Refrigerant is withdrawn from evaporator 2| through pipe 31, control apparatus 38, and pipes 39 and 40, and from evaporator 22 through'pipe 4l, control apparatus 42 and pipes 43 and 40.

The evaporator 2| cools a medium in a cabinet 34 and the evaportor 22 cools a medium in a cabinet 35. In both instances the medium cooled is air. It is desirable to maintain the temperature of the air in cabinet 34 at one temperature and the temperature of the air in the cabinet 35 at another temperature. It is also desirable to prevent the collection 0f an appreciable amount of ice or frost on the evaporators by causing the temperatures of the evaporators to rise above the melting point of ice on each cycle of operation. To maintain the temperatures in the cabinets 34 and 35 accurately and to prevent the collection of an undesirable amount of frost on the evaporatorsthe control apparatuses 38 and 42 are provided for controlling the circulation of refrigerant through the evaporators 2l and 22, respectively. The apparatuses 38 and 42 permit circulation of refrigerant through the evaporators when the temperature of the respective evaporators rises to a predetermined degree above the melting point of ice and terminate the ilow of refrigerant when the temperatures of the air in the cabinets-are lowered to predetermined desired temperatures, or if the temperatures of the air in the cabinets are at or lower than the desired predetermined temperatures, the circulation of the refrigerant is stopped when the temperatures of the evaporators are lowered a pre-- determined degree. The control apparatuses also control the compressor motor 26 to cause operation of the compressor whenever the temperature of either of the evaporators is raised to the predetermined high temperature. The control apparatuses are preferably located where the temperature is always above the temperatures of the evaporators. The control apparatuses 38 and 42 are similar in construction and to clearly illustrate the details thereof the apparatus 38 is shown partly in section in Fig. 2.

Referring to Fig. 2, the control apparatus 38 includes a casing 46, comprising upper and lower sections 41 and 48 that are secured together by screws 49, the joint between the sections being sealed by a suitable gasket. A chamber 50 is formed by these sections, which chamber has `an inlet 52 and an outlet 54. The inlet 52 is connected to the evaporator 2| by pipe 31 and the outlet 54 is connected with the compressor 25 by pipes 39 and 40. A valve seat 56 is formed at the inner end of the outlet 54 and a valve 51 is adapted to close the seat for controlling the flow of refrigerant through the chamber 50. The valve 51 is guided in a cylinder 58 which is vented at 59 to permit free movement of the valve.

The section 41 of the casing 46 includes a cylindrical section 60 closed at the bottom thereof by a wall 6|. A cap 62 is threaded in the upper end of the cylinder 60 and a sealing gasket 63 is interposed between the cap and an annular shoulder of the cylinder. The open end of a bellows 651 is hermetlcally sealed to the bottom wall 6| by' a collar 66 threaded in the lower end of the cylinder, which collar compresses a peripherial iiange of the bellows against the wall 6 I. The upper end another and the spring 94 is disposed between the plates and is connected to pins interconnecting the plates forming the levers. The spring 94 biases the levers 9| and 92 to one side or the other of a dead center position of the levers and spring. The lever 86 is connected to the free end of the lever 92 by a pin and slot connection and the lever 9| is connected to the valve 51 by a pin and slot connection. When the rod 1| is raised and lowered the spring 94 is movedrfrom one side of the dead center of the toggle to the other by the lever 92 and the lever 9| is snapped from the valve closing position to the valve opening position.

The switch 88 is inside the chamber 50, although it may be located on the outside, and it is mounted on a base formed of insulating material. The switch comprises a terminal plate |0| carrying a ilxed contact |03 and a spring strip |04 carrying l a contact |05 that is adapted to close on contact |03. The spring strip |04 is normally biased to separate the contacts |03 and |05. A terminal post |06 is connected with the plate |0| and a terminal post |01 is connected to the spring |04.

. When the valve 51 is moved to the open position of the bellows 65 is closed by a wall 68, which wall is reeniorced by a disc 69. The interior of the bellows is connected with the chamber 60 by an opening 10 in the wall 6|. Thus changes in pressure in the chamber 50 will be transmitted to the interior of the bellows 65, and since the chamber 50 is connected with the evaporator 2| the gas pressure in the evaporator will aect the bellows. Thus the bellows will expand and contract according to changes in pressure in the evaporator, which changes in pressure correspond to changes in temperature of the evaporator.

A rod 1| extends through an opening in the wall 68 and is sealingly attached to this wall by washers 12 and 13. Expansion and contraction oi the bellows raises and lowers the rod 1|, which rod is -guided by a bushing 14 formed on the wall 6|. The rod 1| extends through an opening 18 in the cap 62 and a compression spring 80 is disposed around the rod and rests on the washer 12. A plug 82 is threaded in the opening 10, and is provided with a cylindrical recess for receiving the spring 80 and an opening the top thereof through which the rod 1| extends. The tension of the spring 80 is adjusted by the plug 82, which plug may be locked in any desired adjusting position by a nut 84.

The lower end of the rod 1| is connected with a snap mechanism 85 by a lever 86 pivoted at 181, which snap mechanism is adapted to actuate the valve 51 and a switch 88. The snap mechanism 85 may be of any suitable construction, but in the embodiment shown it is a toggle comprising two opposed levers 9| and 92, pivoted on the tines 931 of a bifurcated post 95, and a spring 94 interconneizt-` ing the two levers.y The levers 9| and 92 are each formed by two .parallel plates spaced from bne the strip |04 is moved to close the contact |05 on contact |03 by a lug ||0 that extends laterally from the valve. The lug |0 is preferably formed of a suitable insulating material and it is secured in a slot through the valve 51 by a screw When the valve is closed the lug H0 is moved from the spring |04and the spring opens the contacts.

The upper end of rod 1|' is connected with a lever by a link |2|, which lever is pivoted on a. post |23. A hook, or catch is formed on one end of the lever |20, which catch is adapted to engage a latch member |26 pivoted on a crank lever |26. A shoulder |30 is formed on the latch |26, which shoulder is adapted to engage with the catch |25 when the rod 1| moves downwardly from its raised position. The edge of the lever |20 opposite the catch |25 and the edge of the member |26 adjacent the shoulder |30 are curved to permit the lever |20 to deflect the member |26 when the lever |20 is moved to the latching position. A pin |32 extends from the member |26 through an opening in the post |23 and the end of the pin is provided with a shoulder |34 for cooperating with the post to limit counterclockwise movement of the latch member |26. A relatively light compression spring |35 is disposed about the pin |32 and between the post |23 and the latch member for biasing the latch member to the latching position. A magnetic coil |36 is mounted on the post |23 and an armature |31 is provided on the member |26 so that when the coil |36 is yenergized the latch member will be drawn clockwise to release the lever |20.

'I'he crank lever |28 is pivoted at |29 and a pin |40 is threaded through the lower end of the crank lever |28, which pin engages an actuating button |42 of a snap switch |43. The snap mechanism of the switch |43 may be similar to that described in the patent to H. G. Leupold, No. 1,780,758, but it is arranged to snap the switch closed when the button |43 is pressed and to snap the switch open when the button is released. Terminals |45 and |46 are provided for connecting the switch in cirlmined temperature. lsuch that the closing temperature. can be sewhich engages the bushing |52. Clockwise movement of the crank lever |28 is limited by lock nuts |84 'and counterclockwise movement of the crank member is limited by nuts |55.

Referring to Fig, 1, the control apparatus 42 is similar to the control apparatus 38 and like parts thereof are referred to by the same reference numerals. The inlet 52 of the control apparatus 42 is connected to one end of the pipe 4| and the outlet 54 is connected to the pipe 43.

The switch 88 of control apparatus 38 is connected in the circuitl of motor 26, which circuit is traced as follows: main |60, motor 26, wire |8|, terminal |01. switch 88. terminal |06, wire |62 and main |83. Switch 88 of apparatus 42 is also connected in the circuit for motor 28 and in parallel with switch 88 of the apparatus 38. The parallel circuit is traced as follows: wires |6| and |64, terminal |08, switch 88, terminal |01 and wires |65 and |62. It is apparent that when either one of the switches 88 is closed the m'otor 28 will operate.

Referring to the control apparatus 38. the circuit for the magnetic coil |36 thereof is controlled by switch |43 and a thermostatic switch |10, which latter switch is disposed inside the cabinet 34 and responsive to the air in the cabinet. The switch |10 may be of any suitable construction, butin the drawings it is shown as a bimetal strip |-1| having =a contact |12 that closes on a fixed contact |13 when the temperature of the air in the cabinet is reduced to a predeter- Preferably the switch is lected. The circuit for the coil |36 is traced as follows: main |60, wire |15, switch |10. wire |16, coil |36, wire |18, switch |43, wires |19 and |62 and main |63. When switches |43 and |10 are closed the magnetic coil |36 is energized for re/ leasing the lever |20. i

Referring to the apparatus 42, the circuit for the magnetic coll |36 thereof is controlled by the switches |43 and |80, the latter switch being subjected to the air temperature of the cabinet 35.

The switch |80 is similar to switch |10 and prefjusted to close at 38 degrees F. and 42 degrees F..

respectively. Since it is desirable to permit the temperature of the evaporators 2| and 22 to rise above the melting point of ice during each cycle of operation to prevent the collection of an appreciable amount of ice on the evaporators. the springs 80 in each control apparatus are adiusted by the plug 82 so that the pressures in the evaporators necessary to expand the bellows 65 to cause opening of the valves ,51, of the respective control apparatuses 38 and 42. will correspond to the pressure of the refrigerant at approximately 33-degrees F. It is understood. however. that the apparatuses could be adjusted to open the valves thereof at any desired temperatures nor is it essential that these temperatures be the i same.

When the temperature of the evaporator 2| rises to 33 degrees F. the pressure of the refrigerant in the chamber of the apparatus 38 will expand the bellows which raises the rod 1| to cause the valve 51 to be opened and the switch 88 to be closed to start the compressor motor 26. As the rod 1| is raised to the valve opening position, the catch |25 of lever |20 biases the latch member |26 clockwise until the shoulder |30 of the latch |26 is over the hook and then the latch |26 is biased to the left to engage the catch. As the temperature of the evaporator 2| is lowered the pressure within the bellows 65 decreases and the spring tends to collapse the bellows and lower the rod 1|. As the rod 1I is lowered toward the valve closing position the lever |20 raises the latch member |26 and causes the crank lever |28 to rotate and close the switch |43. The degree of reduction in pressure in the evaporator 2| required to cause the switch |43 to be closed is determined by thev adjustment of the spring |50. After the switch |43 is closed further movement of crank lever |28 is prohibited by the nuts |54 and further movement of the rod 1| to the valve opening position is prevented. As long as the temperature within the cabinet 34 is above 38 degrees F. the switch |10 will be open and the magnetic coil |36 will not be energized, but when the temperature of the cabinet 34 is lowered to 38 degrees F. the thermostatic switch |10 will close and cause energlzatlon of the magnetic coil |36 which withdraws the latch member |26 from the catch |25 of the lever |20, thereby releasing the rod 1|. When the rod 1| is released the snap mechanism closes the valve 51 and opens the switch 88. Also, when the latch member |26 is disengaged from the hook |25, the crank lever 28 is biased counterclockwise and the switch |43 is opened, thereby deenergizing the magnetic coil.

In the event that after a cooling phase is ini-` tiated in the evaporator 2| and the temperature of the air in the cabinet 34 is reduced to 38 degrecs F. before the switch |43 is closed, the magnetic coil |36 will not be energized until the switch |43 isrclosed. This insures a short cycle of operation which is desirable to cause air circulation in the cabinet.

The control apparatus 42 operates in a similar manner to that described with reference to the apparatus 38, but the apparatus 42 will not close its valve 51 and open its switch 88 until the temperature of the air in the cabinet 35 is reduced to at least 42 degrees F., at which temperature the switch |80 closes the circuit for the coil |36 to release the lever |20.

It is apparent that the control apparatuses 38 and 42 control the flow oi refrigerant from the evaporators 2| and 22 to the compressor 25 independently of one another but the compressor motor 26 is operated as long as the valves 51 of either one of the two control apparatuses is open. By using applicants control apparatus Where a plurality of heat absorbers are supplied with a heat exchange fluid, the temperatures of each one of the heat absorbers and the mediums effected thereby may be accurately controlled.

While the form 0f embodiment of the present .invention as herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

I claim:

1. A refrigerating system comprising in combination, a plurality of evaporators; means for withdrawing gaseous refrigerant from the evaporators, condensing the refrigerant and delivering refrigerant to the evaporators; a valve for controlling the now of refrigerant through one iii of the evaporators; means responsive to pressure changes in said one evaporator for actuating the valve; a second valve for controlling the flow of refrigerant through another of the evaporators; means responsive to pressure changes in said other evaporator for actuating the second valve; and control means actuated by the second v:men-- tioned means for initiating operation of the first mentioned means when the iirst mentioned valve is opened, said control means also being actuated by the third mentioned means for initiating operation of the first mentioned means when the second valve is opened, and said control means being actuated by the second and third mentioned means to terminate operation of the rst mentioned means only when both of said valves are closed.

2. A refrigerating system comprising in combination, a plurality of evaporators; electrically controlled means for withdrawing gaseous refrigerant from the evaporators, condensing the refrigerant and delivering refrigerant to the evaporators; a valve for controlling the flow of refrigerant through one of the evaporators; a switch in the circuit of the first mentioned means; means for opening and closing the valve and actuating the switch in response to pressure changes in the said one evaporator; a second valve for controlling the flow of refrigerant from another of the evaporators; a second switch connected in the circuit of the first mentioned means and in parallel circuit with the first mentioned switch; and means responsive to pressure changes in the said other evaporator for opening and closing the second valve and for actuating the second switch.

Mm 3. A refrigerating system comprising in com- Wbiiiation, a cabinet; an evaporator disposed in the cabinet for cooling a medium in the cabinet; means for withdrawing refrigerant from the evaporator, condensing the refrigerant and delivering refrigerant to the evaporator; a valve for controlling the flow of refrigerant through the evaporator; automatic means for operating the valve between two control positions in accordance with changes in temperature; and second automatic means operable in accordance with the attainment of a predetermined temperat/ure for preventing movement of the valve to one of its control positions by the 4rst mentioned automatic means until the attainment of a second predetermined temperature, one of said automatic means being operable in accordance with changes in the temperature of the evaporator and the other of said automatic means being operable in accordance with changes in the temperature of the medium in the cabinet.

4. A refrigerating system comprising in combination, a cabinet; an evaporator in the cabinet for cooling a medium in the cabinet; means for withdrawing refrigerant from the evaporator, condensing the refrigerant and delivering refrigerant to the evaporator; a valve for controlling the flow of refrigerant through the evaporator; means for opening and closing the valve in accordance with the attainment of predetermined ,temperaturea respectively, of the evaporator; means operable in accordance with changes in the temperature of the medium in the cabinet for preventing closing of the valve by the second mentioned means while the temperature of the medium is above a predetermined temperature; and control means for the first mentioned means, said control means being operated by the second mentioned means.

5. A refrigerating system comprising in combination, a. cabinet; an evaporator for cooling a medium in the cabinet; means for withdrawing refrigerant from the evaporator, condensing the refrigerant and delivering refrigerant to the evaporator; a valve for controlling the ow of refrigerant through the evaporator; means for opening and closing the valve in accordance with the attainment of predetermined temperatures, respectively, of the evaporator; and means operable in accordance with changes in the temperature of the medium in the cabinet for preventing closing of the valve by the second mentioned means while the temperature of the medium is above a predetermined degree.

6. A refrigerating system comprising in combination, an evaporator; means for controlling the circulation of refrigerant through the evaporator including a member and a device for moving the member to different control positions in accordance with changes in temperature of the evaporator; means for preventing movement of the member to one of its control positions; electrically operated mechanism for rendering the last mentioned means inoperative for permitting movement of the member to said one control position; and a switch for controlling the electrically operated mechanism, said switch being actuated by the said device in accordance with the attainment of a predetermined temperature of the evaporator.

7. A refrigerating system comprising in combination, a cabinet; an evaporator for cooling a medium in the cabinet; means for withdrawing refrigerant from the evaporator, condensing the refrigerant and delivering refrigerant to the evaporator; means for controlling the ow of the refrigerant through the evaporator including a control member and a device operable in accordance with the attainment of predetermined temperatures for operating the control member; means for preventing movement of the member to one of its control positions by said device; electrically operated means for rendering the third mentioned means inoperative; a switch for controlling the electrically operated means; and a device operable in accordance with changes in temperature for actuating the switch, one of said operable devices being operable in accordance with changes in the temperature of the evaporator and the other device being operable in accordance with the temperature of the medium in the cabinet.

8. A refrigerating system comprising in combination, a cabinet; an evaporator for cooling a medium in the cabinet; means for withdrawing refrigerant from the evaporator, condensing the refrigerant and delivering refrigerant to the evaporator; means for controlling the Ailow of refrigerant through the evaporator, said means including a movable control member and a device operable in accordance with changes in temperature for actuating the control member; means for preventing movement of the. control member to one of its control positions by said device; an electrically operated mechanism for rendering the third mentioned means inoperative; a circuit for the electrically operated mechanism including two switches, one of said switches being moved to closed position by said device in accordance with the attainment of a predetermined temperature; and a second device operable in accordance with changes in temperature for closing the other of said switches in accordance with the attainment of a predetermined temperature, one of said devices being operable in accordance with changes in the temperature of the evaporator and the other of said devices being operable in accordance with changes in the temperature of the medium in the cabinet.

9. A refrigerating system comprising in combination, a cabinet; an evaporator for cooling a medium in the cabinet; means for withdrawing refrigerant from the evaporator, condensing the refrigerant and delivering refrigerant to the evaporator; a valve for controlling the iiow of the refrigerant through the evaporator; means movable between two positions in accordance with the attainment of two predetermined temperatures. respectively, produced by increase and decrease in circulation of refrigerant through l the evaporator, for opening and closing the valve,

said second mentioned means having a catch; a latching device cooperating with the catch, when the second mentioned means is moved to one of said positions, for preventing movement of the second mentioned means to the other of said positions; a magnet for operating the latch to release said second mentioned means; and a thermally responsive switch for controlling the magnet, said switch being operable in accordance with changes in the temperature of the medium of the cabinet.

10. A refrigerating system comprising in combination, an evaporator; electrically energized means forl withdrawing refrigerant from the evaporator, condensing the refrigerant and delivering refrigerant to the evaporator; a valve for controlling the flow of refrigerant through the evaporator; means operable in accordance with changes in temperatures produced 'by warming and cooling operations of the evaporator for opening and closing the valve, the last mentioned means including a snap mechanism for operating the valve; and a switch for controlling the first mentioned means, said switch being-opened and closed by said snap mechanism when said mechanism closes and opens lthe valve, respectively.

11. A refrigerating system comprising in combination, a cabinet; an evaporator for cooling a medium in the cabinet; electrically operated means for withdrawing refrigerant from the evaporator, condensing the refrigerant and delivering refrigerant to the evaporator; a valve for controlling the flow of refrigerant through the evaporator; a switch for controlling said means; snap acting mechanism for operating the valve and switch; automatic means for actuating said mechanism, said automatic means having a catch; a latch device cooperating with the catch when the valve and switch are moved to one control position by the automatic means, for preventing movement of the valve and switch to another control position by the automatic means; a magnet for operating the latch to release the catch; a switch for controlling energization of the magnet; and automatic means for actuating the last mentioned switch, one of said automatic means being operable in accordance with temperature changes in the evaporator and the other automatic means being operable according to changes in temperature of the medium.

12. A refrigerating system comprising in combination, an evaporator; electrically operated means for withdrawing refrigerant from the evaporator, condensing the refrigerant and delivering refrigerant to the evaporator; a valve for controlling the owof refrigerant through the evaporator; a switch for controlling said means; snap acting mechanism for operating the valve and switch; a second means'rnovable between two positions in accordance with the attainment of two predetermined temperatures respectively, of the evaporator for actuating said mechanism, said second mentioned means having a catch; a latch cooperating with said catch,I when the second mentioned means is moved to one of said positions for preventing movement of the second mentioned means to the other of said positions; a magnet\ for operating the latch to release said second mentioned means; a circuit for the magnet; a switch in said circuit, said second mentioned switch being moved to closed position after a predetermined movement of the said second mentioned means from said one position toward said other position,

13. A refrigerating system comprising in combination, a cabinet; an evaporator for cooling a medium in the cabinet; electrically controlled means for withdrawing refrigerant from the evaporator, condensing the refrigerant and delivering refrigerant to the evaporator; a switch for controlling said means; automatic means operable in accordance with changes in temperature for actuating the switch; means for preventing movement of the switch to one of its control positions by said automaticA means; electrically operated means for rendering the third mentioned means inoperative; a switch for controlling said electrically operated means; and automatic means operable in accordance with the attainment of a predetermined temperature for actuating the last mentioned switch, one of said automatic means being operable in accordance with changes in the temperature of the evaporator and the other of said automatic means being operable in accordance with changes in the temperature of the medium.

14. A refrigerating system comprising in combination, a cabinet; an evaporator for cooling a medium4 in the cabinet; electrically operated means for withdrawing refrigerant from the evaporator, condensing the refrigerant and delivering refrigerant to the evaporator; a switch for controlling operation of said means; automatic means operable in accordance with changes in temperature for actuating the switch; means for preventing movement of the switch to one of its control positions by said automatic means; electrically operated mechanism for rendering the third mentioned means inoperative to permit movement of the switch to said one position by said automatic means; a switch for controlling the electrically operated mechanism, said second mentioned switch being closed by said automatic means in accordance with the attainment of a predetermined temperature; a second switch for controlling the electrically operated mechanism; and automatic means for operating the last mentioned switch in accordance with changes in temperature, one of said automatic means being operable in accordance with changes in the temperature of the evaporator and the other of said automatic means being operable in accordance with changes in the temperature of the medium.

15. A refrigerating system comprising in combination, a cabinet; an evaporator for cooling a medium in the cabinet; electrically operated means for withdrawing refrigerant from the evaporator, condensing the refrigerant and delivering refrigerant to the evaporator; a switch tioned means; a magnet for operating the latch for controlling operation of said means; means to release the second mentioned means; a circuit for actuating the switch in accordance with the `for energizing the magnet; and means operable attainment of predetermined temperatures; in the in accordance with changes in the temberature evaporator, said second mentioned means having 5 of the medium in the cabinet for controlling the a catch; a latch mechanism cooperating with said circuit.

catch for preventing movement 0f the switch to PAUL HAYMOND. one of its control positions by the second men- 

